from gwyneth paltrow to zooey deschanel, celebrities squaring off gluten. along with millions of other americans. but is it any healthier to go gluten-free? the latest craze feeding a multibillion-dollar industry now facing some tough questions. >>> and -- ♪ encore performance. michael jackson appears live at the billboard music awards with a brand new song. how did that happen? but first, the "nightline" five. ♪ ♪ [ barks ] whoo! mmm! ♪ ♪ oh, yeah [ whistling ] [ male announcer ] discover your new orleans. start exploring at followyournola.com. [ woman ] and i love new orleans! >>> good evening. the average price tag for a year of college now over $30,000. so for many students that can mean years of massive debt. but you're about to meet some enterprising young women and men who've chosen a different path. one that involves a few nights a week of industrious work. and did i mention it includes taking their clothes off? here's my "nightline" co-anchor juju chang. >> most of my classes they're discussions -- >> reporter: maggie looks very much like the strai

she was in the elevator with zooey deschanel, reese witherspoon and who do you make

celebrities like gwyneth paltrow and zooey deschanel are gluten free.ry stores are laden with gluten-free products. it is big business, very big. the u.s. gluten-free market is predicted to reach $6.6 billion by 2017 and a new study finds many people who say they are sensitive or intolerant to gluten probably aren't. >> this has really become a fad. >> reporter: dr. suzanne steinbaum is director of women's heart health at lenox hospital in new york city. >> people have grabbed on to the gluten free issue because they think it is healthy, but this is a trend and it's going to leave as quickly as it came. >> reporter: before it goes, let's find out what is gluten? well, it is a combination of two proteins found in wheat, rye, barley and other grains, and in soups, salad dressings and sauces, too. there are people, about one in 133, who are born with a genetic disorder called celiac disease that makes them truly unable to tolerate gluten. many people who don't have celiac disease but suffer from gluten sensitivity have gone gluten-free and they love it. th

from gwyneth paltrow to zooey deschanel, celebrities squaring off gluten.dollar industry now facing some tough questions. >>> and

es de la marca de zooey deschanel.Í es donde se separan los hombres de los niÑos. tienes el micrÓfono ahÍ. vamos a cantar. ahora vamos a interpretar otra canciÓn. "nada es para siempre". ¿quÉ significa? >> para mÍ, esa frase es una frase muy importante. yo creo que hay que ver el lado positivo de esa frase. hay que aprovechar cada dÍa. hay que amar cada dÍa como si fuese el Último. no podemos dejar para maÑana ese amor que sentimos o decir te amo, te queremos. para mÍ, es muy poderosa. y esta canciÓn, tiene esa parte que tambiÉn hay que gritar de vez en cuando. ♪ ♪ ♪ te quiero hoy ♪ yo quiero abrirle al corazÓn una ventana ♪ ♪ esto es amor y es tan grande que no acaba en mis palabras ♪ ♪ yo quiero amarte ♪ yo quiero amarte hoy ♪ por si no hay maÑana ♪ yo quiero amarte hoy ♪ yo quiero amarte hoy ♪ por si no hay maÑana >> fuerte el aplauso. definitivamente estamos viviendo un momento mÁgico. ¿quÉ les quiere decir a ellos? >> muchas gracias. aprovecho para dar las gracias por organizar esta fiesta hermosa. no todos los dÍ